The present invention relates to diving masks of the type used in scuba diving or skin diving, and particularly to optical systems and configurations that seek to expand the diver""s field-of-view underwater.
There have been many attempts to either increase underwater field-of-view, or to achieve true-size viewing underwater. Some prior art make claims that their inventions achieve both unmagnified vision and expanded field-of-view underwater such as U.S. Pat. No. 5,777,712, Sansalone; U.S. Pat. No. 3,040,616, Simpson; U.S. Pat. No. 5,523,804, Nolan. The aforesaid patents simply do not work as claimed. Other designs try to achieve panoramic views by curving the clear window in a fashion with no regard for optical consequences such as EP 0824029, Beltrani; U.S. Pat. No. 5,564,132, Kuo; U.S. Pat. No. 5,502,515, Sansalone; U.S. Pat. No. 3,483,569, Armendariz and U.S. Pat. No. 2,876,766, Rebikoff et al. These last five designs, while making claims to be free of distortion, do in fact produce prodigious amounts of distortions in size, shape, focus distance, resolution and color fringing. Patents for various positive meniscus lens configurations include U.S. Pat. No. 5,625,425, Kranhouse and U.S. Pat. No. 3,672,750, Hagen; these designs are able to achieve a wider field-of-view with reasonable resolution, however the image magnification effects of water is not entirely eliminated.
Attempting to produce both true size and panoramic vision, U.S. Pat. No. 3,899,244, Mulder is for a twin lens design comprised of a front dome and a rear converging element. A unique feature of this patent is the tilting of the two optical lens systems relative to each other as a means to increase field-of-view angle. However ray-trace analysis of this design indicates severe distortions and aberrations, aggravated by the fact that forward vision is not through the axial center of the lens system.
Using multiple panes of flat lenses of flat lenses does increase the field-of-view, as disclosed in U.S. Pat. No. 5,345,615, Garofalo, however this mask falls short of providing satisfactory results due to the extreme fragmentation of image experienced when used underwater.
Of all prior art, a most notable design for achieving true size underwater is U.S. Pat. No. 2,730,014, Ivanoff. This patent involves a reverse-Galilean telescope design, behind a flat port; however, true size is achieved with a very limited field-of-view. (by reverse-Galilean telescope, we mean a diverging lens, followed by an air space and a converging lens.) This design proved that underwater eye-hand coordination is greatly improved if the magnification effects of water can be eliminated, but panoramic vision was highly desirable.
Therefore it would be highly advantageous to provide a dive mask having both a wide field-of-view as well as achieving true size underwater, with no apparent distortions.
The present invention is for an improved optical arrangement that both increases field-of-view and achieves true size representation of objects underwater, without the effects of magnification caused by water""s refractive index. Low levels of distortions and high resolution is achieved with this design.
The optical system as designed is a pair of afocal reverse Galilean telescopes behind a domed window. One afocal reverse Galilean telescope is positioned in front of each eye.
The distortions of this system, if produced as intended and as described herein, are so minimal so as to allow tilting the entire optical systems relative to each other in the horizontal axis, so as to achieve a more panoramic view.
A major improvement of all these designs over prior art is achieved by tilting the lenses relative to each other, with little deleterious effect on optical performance as perceived by the diver. This tilting provides for a reduced lens package and better mechanical clearance for the optics around the bridge of the nose of the diver, as well as providing more mechanical clearance between the left and right lens barrels.
Starting from the water side of the optical system is a dome shaped lens in contact with water. This dome lens may or may not have positioned in front of it a thin lens as described in U.S. Pat. No. 5,764,332 (Kranhouse) for improving above water vision. The next optical element in the lens system, further from the water side, is a diverging lens or diverging lens group. Continuing closer to the eye of the diver is a converging lens or converging lens group.